Delay line for travelling-wave tubes

ABSTRACT

A delay line for travelling-wave tubes, comprising a hollow guide with successive transversely disposed discs having elongated attenuation members which project into the interior of the hollow wave guide, with the longitudinal axes of such attenuation members extending at least approximately parallel to the longitudinal axis of the delay line and mechanically firmly supported in recesses in the transverse discs. The attenuation members are retained by a press or force fit with the transverse discs, and may be provided in the portion thereof surrounded by the associated transverse disc with at least one notch which extends transversely to the longitudinal axes of the members and which is at least partially filled with the ductile material of such associated transverse disc.

BACKGROUND OF THE INVENTION

The invention relates to a delay line for travelling-wave tubes,comprising a hollow guide provided with successive transverse discsformed from a ductile material, which discs have at least one centralopening for the passage of the electron beam and provided withrespective attenuation members which extend into the hollow guideinterior and have their longitudinal axes extending at leastapproximately parallel to the longitudinal axes of the delay line. Therespective attenuation members are each mechanically rigidly mounted ina cooperable recess formed in the associated transverse disc. Theinvention also relates to a method for producing a delay line of thistype.

A delay structure of the general type referred to is known from GermanPat. No. 23 47 209, corresponding to U.S. Pat. No. 3,924,151, with theconstruction therein disclosed utilizing cylindrical attenuation memberswhich are soldered into the transverse walls, each of which isadditionally provided with a coupling opening or slot therein. Whileattenuation cylinders secured by a soldering operation are rigidlymounted in the desired operative positions, as has become apparent,completely exact reproducible attenuation values cannot be achieved asthe solder spreads out during the soldering operation, in particular, onthe metallized areas of the attenuation cylinder involved, and thusoperatively loads the individual cells to an extent that is notcompletely controllable.

SUMMARY OF THE INVENTION

In accordance with the invention, to eliminate such problem in a delayline of the type initially described, the attenuation members aresupported in the cooperable transverse discs by a press or force fit,and each member is provided in the portion thereof surrounded by theadjacent portion of the associated transverse disc, with at least onenotch which extends transversely to the longitudinal axis of the memberand which is at least partially filled with the ductile material of theassociated transverse disc. As a general rule, transverse discs of delaylines, of the type involved, are constructed of copper or of an alloyutilizing a copper base, and the cooperable attentuation members arecylindrically formed.

To insure the flow of ductile material into the notch of the attenuationmember, preferably the attenuation member, which has previously beenformed with the desired notch, is initially inserted, i.e. pushed, intothe recess of the corresponding transverse disc. The latter isthereafter compressed in axial direction in an annular area which issubstantially concentrically disposed relative to the axis of theassociated attenuation member and thus surrounds the same. As a resultof such simple compression operation the outer diameter and wallthickness of the transverse disc remains substantially unaffected. Withsuch a force fit, providing a direct interlocking of the attenuationmember with the associated disc, the attenuation members are reliablyand very efficiently mounted without the use of additional bondingmaterials or the like which would have an influencing effect on the tubecharacteristics. In addition, irrespective of different coefficients ofthermo expansion between the copper disc and a ceramic attenuationbodies, the latter cannot become loose even with large temperaturefluctuations. Further, the heat, due to energy losses, which is normallydeveloped in the attenuation elements, is relatively effectivelydissipated. The advantages of an attachment of an attenuation member inaccordance with the present invention is of particular importance inconnection with relatively thinwall discs which present, to theattenuation member, contact surfaces of only slight width, i.e. in thedirection of the thickness of the disc.

While the use of a mere press fit between an attenuation cylinder,carried by a transverse vane disposed between two cell-formingtransverse walls is known, copending application with U.S. Ser. No.693,840, filing date June 8, 1976, same inventor such concept merelyinvolves a pressed insertion of the cylinder into a bore, i.e. as aresult of an interference fit.

Advantageously, the attenuation members, in accordance with thepreferred embodiment of the invention, have the notch portion thereofextending, in the axial direction of the member, a distance equal toapproximately one-half the corresponding thickness dimension of theassociated disc.

It is particularly favorable to provide each of the attenuation memberswith two, axially spaced, annular grooves, their respective edges ofwhich closest to the corresponding ends of the attenuation member beingspaced apart a distance equal to the corresponding thickness of theassociated disc, whereby such edges are substantially flush with theannular portions of the disc faces encircling the associated member. Inthis construction relatively low pressures are sufficient to effect asufficient material flow to fill up the respective grooves as thetransverse disc, when pressure is applied from opposite sides thereof,is deformed to the greatest extent at opposite faces adjacent the edgesat the notched portions of the attenuation member. Tests have revealedthat even with extremely thin copper discs, whose wall thickness isconsiderably less than the diameter of the attentuation cylindersinserted therein, a rigid cylinder mounting existed even after repeatedheating up of the structure.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be more specifically explained in connection with thepreferred illustrative embodiment disclosed in the drawing, in which thesingle FIGURE merely represents a longitudinal sectional view of aportion of a delay line, sufficient for an adequate explanation of theinvention.

DETAILED DESCRIPTION

Referring to the drawing, there is illustrated therein a fragmentaryportion of a delay line, merely three transverse discs thereof beingillustrated, with the travelling-wave tube involved being adapted forthe amplification of millimeter waves. The delay line thus comprises aplurality of aligned discs 1 and 2, constructed, for example, of copperand disposed in alignment one behind the other, in the direction of theelectron beam, with the discs being assembled in a stacked arrangementto form a unitary structure. Each disc is provided with a peripheralannular flange or wall 3, the outer end edges of which abut the adjacentdisc, whereby each disc functions as a transverse wall 5 operative todefine successive cells.

Each of the transverse walls 5 is provided with a central opening 6 forthe passage of the electron beam, as well as a coupling opening 7 whichis radially disposed with respect to the central opening, with eachsuccessive line disc being rotated about its axis through 180°, wherebycorresponding alternate and intermediate discs have the couplingopenings thereof extending in aligned relation. Each pair thusconstitutes a period of the delay line, with the line so formed having abackward-running fundamental wave in the longest wave length band, andit is thus operated in the first forward running space harmonic, i.e.,between the pi and 2 pi points.

Each of the transverse walls 5 is provided with a recess 8 therein, witheach recess being disposed in opposed relation to the adjacent couplingopenings 7. In the construction illustrated, each recess comprises abore extending completely through the associated wall, with a cooperablecylindrically shaped attenuation member, i.e. attenuation cylinder 9extending therethrough and thus projecting at opposite sides of theassociated wall. Such attenuation cylinders may, for example, be formedfrom tungsten, aluminum oxide, berillium oxide or aluminum oxide.

Each attenuation cylinder is illustrated as being provided with twospaced annular shaped grooves 10 therein which are positioned in theportion of the member encircled by the transverse wall 5. If will benoted that the axially outermost edges of each cooperable pair ofgrooves are axially spaced a distance equal to the correspondingthickness of the wall 5 whereby such edges terminate approximately flushwith the opposite faces of the transverse wall.

Installation of the respective attentuation members is achieved in thefollowing manner. A cylinder is initially inserted into thecorresponding recess of a wall 5, following which such wall is disposedbetween tubular pistons or rams which extend over the projecting ends ofthe attenuation body and engage the transverse wall adjacent suchattenuation member. Upon the application of pressure, the transversewall is thereby placed under compression, whereby the ductile materialthereof will flow into the respective grooves of the attenuation memberto provide a rigid interlocking engagement of the wall with theattenuation member.

Further details with respect to the construction and manufacture of sucha delay line, as well as with respect to the selection of the materialtherefore, may be found in the previously referred to patent.

It will be appreciated that the invention is not limited to the specificdelay line construction illustrated. For example, it is immaterialwhether the attenuation members are supported by transversely extendingcell-defining walls or transverse vanes disposed therebetween. Likewise,the invention is equally applicable to the mounting of attenuationmembers which are inset into bottomed recesses as distinguished from thebores illustrated which extend completely through the supporting walls.However, it will be appreciated that bores, such as illustrated in thisdrawing, have the advantage that a single attenuation member can beemployed for simultaneously attenuating two adjacent cells, and inaddition, the two adjacent cells can be provided with arbitrarilydifferent attenuation loading, utilizing merely a single attenuationmember.

It will further be noted that the invention enables a free selection ofmaterials for the attenuation member and the delay line, requiringmerely that the transverse discs can be sufficiently deformable underits application of pressure, to create the desired material flow intothe grooves of the attenuation member. In addition to copper, alloyssuch as berillium-copper, for example, can be employed for the discstructures.

Having thus described my invention it will be obvious that althoughvarious minor modifications might be suggested by those versed in theart, it should be understood that I wish to embody within the scope ofthe patent granted hereon all such modifications as reasonably, andproperly come within the scope of my contribution to the art.

I claim as my invention:
 1. A delay line for travelling-wave tubes,comprising a hollow guide provided with successive transverse discs of aductile material, each of which has at least one central opening for thepassage of the electron beam, and supports an elongated attenuationmember which projects into the hollow guide interior, with thelongitudinal axes of the respective attenuation members extending atleast approximately parallel to the longitudinal axis of the delay lineand rigidly mechanically mounted in respective recesses formed in theassociated transverse disc, each attenuation member being secured in theassociated disc by an interlocking pressed fit, with the portion of suchmember encircled by the associated disc having at least one notch whichextends transversely to the longitudinal axis of the member, and whichnotch is at least partially filled with the ductile material of theassociated disc.
 2. A delay line according to claim 1, wherein thenotched portion of the respective attenuation members extends, in axialdirection, for approximately half the thickness of the disc thereat. 3.A delay line according to claim 1, wherein each attenuation member isprovided with a pair of spaced notches, each in the form of an annulargroove, both of which are disposed within the recess of the associateddisc.
 4. A delay line according to claim 1, wherein each attenuationmember is provided with a pair of spaced notches, each in the form of anannular groove, and said recess in the associated disc is in the form ofa bore extending therethrough, the respective outer edges of suchgrooves, in each case terminating flush with the respective adjacentouter surfaces of the disc thereat.